1. Field of the Invention
The present invention relates to processing using a laser beam, and to, for example, a method of mounting circuit parts on a printed circuit board by solder welding with lead free solder in particular using a laser, and the like.
2. Description of the Related Art
A method of mounting various types of parts (quartz oscillators, ICs, resistors, capacitors, etc.) on a printed circuit board by laser welding with solder is known. Although these various types of the parts are connected to the printed circuit board through the connecting terminals of the parts, the connection terminals of the parts are disposed with variations in orientation and interval. Accordingly, heretofore, the respective parts are connected to the printed circuit board by sequentially laser welding at a plurality of connecting portions in such a manner that connecting portions where solder is deposited are irradiated with a single laser beam one after another by moving the board or scanning the laser beam across the board (for example, refer to Japanese Unexamined Patent Application Publications Nos. 2002-1521, 10-256717, 09-199845, and 08-279529).
However, the known methods have the following drawbacks. That is, for irradiating processing portions (including welding portions) with a laser beam, a stage which carries the parts mounted atop a printed circuit board needs to be moved and turned arbitrarily in plane. However, such stage control is hardly practical when it comes to placing the laser welding into mass production lines. This is because it is terribly difficult to translate a heavy stage in a quick motion according to various directions and intervals of the connecting portions. Actually, printed circuit boards and parts to be mounted on the circuits are supplied in one direction in most mounting applications.
On the other hand, scanning the laser beam with a galvanometric mirror, can avoid the above problem. In this case, however, a space in which the mirror is placed is necessary in addition to the hardware and software cost of using the galvanometric mirror, which is a negative factor for making it difficult to introduce the laser joining technology into manufacturing settings. Further, since heating a plurality of processing portions sequentially by the laser beam irradiation adds to processing time as opposed to the case in which they are simultaneously heated by the laser beam irradiatation. Thus, a problem also arises in that a laser beam utilizing efficiency is rather limited due to the heat dispersion during the irradiation.
An object of the present invention, which was made to solve the above problems, is to provide a laser welding method and a laser welding apparatus capable of efficiently as well as effectively connecting various types of parts such as electronic parts and the like to a printed circuit board by a simple arrangement, so as to mount them on the board. Further, another object of the present invention is to provide a laser processing method and a laser processing apparatus that employs the same principle as that of the above welding method is applied to other kinds of processing such as drilling, cutting, texturing and modifying and the like and that allows laser irradiation points to be easily targeted during the above processing.